Categories
Blog Geography Secondary Teaching Weather

Air Masses

In this article we explore air masses – the idea that, by looking at where our wind is blowing from, and what has happened to the air in the wind on its way to use, we can begin to understand why we’re getting some particular weather.

We live on an island, and the weather can come at us from any direction, although in practice, it comes from some directions more than others  – this wind rose shows the direction the wind was recorded coming from at Heathrow airport, near London. The longer the bar, the more often the wind came from that direction, so you can see that our wind comes from between southwest and west most often.  

Lets take a step back and remember that warm air rises – whether that’s the air being heated in a hot air balloon or the air above a radiator (watch a simple demonstration).

What happens to the rising air? As it rises it cools. Cloud and rain are caused by warm air rising, warm air rising is called convection (watch a simple demonstration).

You can often see convection going on in the atmosphere – you get puffy cumulus clouds, with flattish bases and puffy tops where the cloud is bubbling up.

clouds

More generally, Clouds form when there is more condensation going on than evaporation in the atmosphere.

The colder it is, the less evaporation happens – so cloud forms when the air cools.

This isn’t just when warm air rises.

Now we can think about air masses, they are classified according to where they have come from, and what they have passed over:

One air mass generally covers the whole country.

However, it can bring different weather conditions to different places. For example, Tropical continental air can carry Saharan dust, but it mostly falls on the south of the UK – there isn’t much left in the air by the time it reaches Scotland.

Lets consider Polar maritime (Pm) air first (click on the map to start the animation):

Polar maritime air comes towards us from further North in the Atlantic. It starts cold, but is slowly warmed by the ocean below as it travels over progressively warmer water. It also picks up moisture from the ocean. 

As it is warmed, it becomes more unstable and inclined to rise, leading to convection and puffy Cumulus clouds, mainly over the ocean. As the air hits land (the western coast of Ireland, Wales, Scotland and England) the air, which was already inclined to rise, is forced up a bit more – forming more cloud, and giving rise to rainfall. 

Polar maritime air, our dominant air mass, brings cloud and rain to the west of the UK and relatively dry air to the east. 

This satellite image is typical of Pm air – you can see the puffy cumulus clouds over the ocean, and the belt of cloud over the western side of the country.  

Returning Polar maritime air (rPm) is air which is Polar in origin but which swings round to hit the UK from the west or even slightly south of west – but if you were to follow its path back, you would see that it was Polar. 

Arctic maritime (Am) air is extreme Polar maritime air, coming down to the UK straight from the north, over the Arctic ocean. It tends to bring wintry weather to Scotland and isolated snowy showers further south, triggered by air rising over the local orography. 

Polar Continental (Pc) air will also be cold to start with and get progressively warmer as it moves south, so you would also expect convection. However, the air will be very dry as it passes over continental Europe, so little cloud will form. The UK is a set of islands though and to reach us, the air must pass over the North Sea, picking up water vapour as it does so. The cloud and precipitation (typically snow in winter) it brings therefore primarily affect the east coast. The longer the path it takes over the North Sea, the more precipitation there will be. 

This satellite image is typical for Pc air – you can see the cloud free areas immediately to the west of the land masses, with cloud forming further east (ignore the front to the west of the UK and Ireland).

Of course, the characteristics of the air masses can be very different in the summer and the winter. Siberia, for example, is extremely cold in winter but relatively warm in summer – so a polar continental air mass can bring us bitterly cold weather and heavy snowfall (for eastern counties) in the winter, but much warmer weather in the summer.

The processes at work in Tropical Maritime (Tm) air are a bit different. This is warm air, which is being cooled from below as it moves north. You therefore wouldn’t expect any convection with air rising, cooling and forming cloud. However, the air is being cooled just by moving north and so eventually may reach the temperature at which cloud forms – flat, featureless sheets of stratus cloud because, on the whole, the air is staying at the same level.

As it is maritime air, there is plenty of water vapour available to form cloud droplets. The processes which give us big, fat raindrops are mainly associated with the vertical air motion and circulations in cumulus clouds. So Tm air at best gives a persistent drizzle.

The satellite image below shows the extensive sheet of stratus cloud over the Atlantic associated with Tm air.

We rarely experience Tropical Continental (Tc) air – air that flows up from the Sahara over continental Europe.  This is the warmest and driest air we can get – any moisture picked up over the Mediterranean will be rained out before it reaches us.

Tc air gives clear skies, as you can see in the satellite image below – again ignore the front to the west of the UK. In the summer, this can mean that some areas get particularly warm – maybe because of their colour (dark) or aspect (facing the Sun) – giving rise to late afternoon localised thunderstorms

A front is where two air masses meet. In the UK, the weather fronts associated with depressions usually separate polar and tropical maritime air.

If there is a front, then different parts of the UK can be experiencing different air masses. The weather on the fronts themselves is more extreme. 

Look out of the window now – what cloud types can you see? Does that tell you anything about where the air is coming from? You can have a look at earth.nullschool to see if you are right.

 

 

Categories
Climate Change Extreme weather Geography Secondary

New Teaching Resource – Salt Marsh Evidence

We have just added a new resource to our Weather and Climate: a Teachers’ Guide collection in the Changing UK Climate section. 

The resource provides students with source material, graphs and maps to allow them to make a poster explaining how salt marshes can protect coastal areas from the impact of rising sea levels. 

Steart Marshes – designed for adaptation to climate change.

Categories
Climate Change Rain Secondary

Exploring Amazon Rainfall data

deforestation

We are delighted to have worked together with the RGS to produce a resource for A Level geography students, using key data skills to investigate the impact of Amazon deforestation on rainfall. 

The worksheet is designed to highlight the importance of meteorology understanding in physical geography. There are activities on the statistical tests of Mann Whitney U-Test and Spearman’s Rank Correlation Coefficient.

Categories
Books Climate Climate Change CPD Geography Microclimates Schools Secondary Teaching Weather

Weather and Climate: a Teachers’ Guide

weather and climate teachers guideIn this teachers’ guide and the accompanying online teaching resources, we aim to give UK geography teachers all that they need to deliver relevant, engaging and thorough weather and climate lessons to 11–14+ year old students. They are not linked to any specific curriculum but should be easily adaptable to all.

The book is accompanied by high quality online background information/professional development resources for teachers.

 

 

 

The Royal Meteorological Society believes that:

  • all students should leave school with basic weather literacy that allows them to understand the weather that affects them, their leisure activities and the careers they choose to follow
  • every student should leave school with basic climate literacy that would enable them to engage with the messages put forward by the media or politicians and to make informed decisions about their own opportunities and responsibilities.

To this end, we have embedded a climate change thread throughout the online resources, showing its relevance to both weather and climate. An understanding of weather and climate is fundamental to an understanding of climate change.

There is a progression of knowledge through the topics, supported by review and assessment activities. The resources also progressively develop key geographical skills such as data, mapwork, GIS, fieldwork and critical thinking.

In this guide, we include common misconceptions which should be challenged in the classroom.

There are 20 topics or chapters. Across these, there are three threads or paths which can be taken through the online resources, depending on the teaching time available:

Basic weather: Weather in our lives, weather measurements, weather and climate, global atmospheric circulation, global climate zones, air masses, pressure and wind and water in the atmosphere

Climate: Weather and climate, global atmospheric circulation, global climate zones, past climate change, polar climate, hot deserts, changing global climate, UK climate, changing UK climate, the climate crisis

Extending weather: Anticyclones, depressions, microclimates, urban weather, tropical cyclones.

Many of the online teaching resources are available with standard or easier versions, as well as extension or alternative activities.

Find the scheme of work, teaching resources, background information for teachers, as well as the Teachers’ Guide (copies of which may be printed on request), here

All the online resources will be updated and revised regularly.

Categories
Geography Secondary Weather

The Weather of 2020

Last week, Sylvia Knight from the Royal Meteorological Society gave a talk for Geography education online on the Weather of 2020.
This year it felt like we had summer weather in Spring and Autumn weather in Summer. In this session, we examine the global processes that determine the weather in the UK, as well as the impact of COVID-19 on weather and climate around the world.
The talk is aimed at A Level students, but would also be useful CPD for geography teachers or for younger students who have already covered a weather topic.

Categories
Geography Rain Secondary

A Level Data Skills: Deforestation and Weather

In a paper that came out in the journal Nature Communications, Self-amplified Amazon forest loss due to vegetation-atmosphere feedbacks, scientists revealed that deforestation can intensify droughts, compounding climate change linked changes in rainfall patterns.

Using data collected by scientists in the School of Earth and the Environment at the University of Leeds, we have created a data skills exercise for A Level geography which allows students to explore leaf area, evapotranspiration and temperature data using various statistical techniques to explore the relationship between deforestation and weather.

With clear links to both the carbon and water cycles, you can find the resources here.

Categories
Geography Secondary

Rainforest deforestation, the carbon and water cycles

Several recent research papers have investigated the impact of rainforest deforestation on local rainfall and temperature.

Find some teaching resources linked to the animation above here.

Categories
Geography Secondary Teaching

Climate Negotiations wins Scottish Award

SAGT awardThe Society’s Climate Change Negotiations for Schools Resource – ‘Simulating a World Climate Conference’ – has been recognized and ‘Highly Commended’ at the SAGT Conference Awards 2018 hosted by Dollar Academy. Morven Neil, RMetS Scottish Education Representative was in attendance at the conference to receive the award and to run a number of seminars that gave conference attendees the opportunity to trial the resource. In these seminars, a number of Geography teachers from across Scotland worked together in designated country groups to decide their own greenhouse gas emission pledges, deliver these to the other assembled delegates and then negotiate. Despite some intense negotiation, they were not able to commit to emission reductions which would limit global temperature increases to within the recommended threshold, but will hopefully leave equipped to confidently deliver the resource in their own classrooms.

Categories
Climate Change Geography Secondary

Water Cycle Film

We are delighted to have produced this short video illustrating how deforestation has an impact on the water cycle, both locally and globally. Bringing together the carbon and water cycles, it is particularly relevant to A level geography (and GCSE biology).

Categories
Geography Secondary

KS3 Weather and Climate Scheme of Work

We have worked hard over the summer to update and improve our resources for KS3 geography, making them more relevant to the new(ish) National Curriculum.

You can find the new suggestions for a weather and climate scheme of work at metlink.org/secondary/key-stage-3/. It includes a number of engaging, interactive lesson ideas.

If you have any comments or suggestions, please contact us at education@rmets.org